Finance, trading & credit calculators that actually model risk.

Calculator.surf is a focused collection of HTML5 calculators built for real decision-making: mortgages, auto loans, and futures risk with stress scenarios and transparent assumptions.

Client-ready outputs

No tracking, no sign-up

Scenario grids, not just one number

Open Mortgage Stress Test → Start with Auto Loan

All calculators run purely in your browser. No data is sent to any server.

Available calculators

All built with the same dark UI system and scenario logic.

Real estate • DSCR

Mortgage Stress Test & DSCR

Model monthly payment, free cashflow and DSCR under interest-rate shocks. Visualize where the loan fails on coverage.

Inputs: loan, income, outgoings, rate shocks Output: DSCR grid by rate

Open calculator →

Built for investors & underwriters

Crypto futures • Risk

Futures Liquidation & Margin Risk

Approximate liquidation levels, margin remaining and thin-margin zones across adverse price scenarios for long and short isolated positions.

Inputs: side, entry, size, lev, margin Output: margin grid vs PnL

Open calculator →

Exchange-agnostic approximation

Auto finance • Retail

Auto Loan Payment & Affordability

Quote monthly payments, total interest, and affordability against income. Factor in downpayment, trade-in, tax and fees in one view.

Inputs: price, DP, tax, APR, term Output: payment + DTI signal

Open calculator →

For dealers, brokers & buyers